Cap and closure device

ABSTRACT

This cap has a cap body having a top plate and a cylindrical portion that drops vertically form the circumferential edge thereof. A knurl portion and a non-knurl portion are formed in the cylindrical portion so as to be arranged in the circumferential direction. A knurl portion vent hole is formed in the knurl indentation and a non-knurl portion vent hole is formed in the non-knurl portion. The non-knurl portion vent hole has a circumferential length that is longer than that of the knurl portion vent hole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cap that seals a container opening and a closure device that uses this cap.

Priority is claimed on Japanese Patent Application No. 2004-289274, filed Sep. 30, 2003, the content of which is incorporated herein by reference.

2. Description of Related Art

Conventionally, a cap that seals a container opening has a metal cap body comprising a top plate and a cylindrical portion that drops vertically from the circumferential edge thereof, and a liner that is provided on the inner surface of the top plate.

An example of this type of cap is one in which a knurl portion on the upper part of the cylinder portion and vent holes formed in the indentations of this knurl portion (refer, for example, to Japanese Examined Patent Application, Second Publication, No. S56-30266).

This cap has a threaded portion formed on the cylinder portion and is coupled to the container opening by covering the container opening with the pre-coupled cap and pressing the cylinder portion inward with the threaded portion formation roller of a cap coupling device.

Generally, in cases when a cap is used to seal the container again after the container has been opened (below, referred to as “resealing”), the pressure in the container can become high, for example, to fermentation in the liquid content. In this case, the cap is pressed upward from the inside due to the internal pressure, and when the container is opened, the cap may easily become separated from the container.

Because the vent holes are formed in the cap, during the opening of the cap, it is possible to vent the gas in the container from the vent holes to the outside of the cap smoothly.

However, with the conventional cap, due to the length of the vent holes formed in the knurl portion, when the user grasps and rotates the cap, the fingers can catch the edge portion of the vent holes causing the user to experience discomfort.

In addition, when the cap is coupled to the container opening, the cylinder portion sometimes deforms at the knurl portion due to the pressure applied to the cylindrical portion when forming the threaded portion.

In consideration of the problems described above, it is an object of the present invention to provide a cap and closure device that can prevent the pressure in the container from rising excessively after resealed, causes no experience of discomfort to the user, and further, can prevent deformation of the cylinder portion.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a cap that provides a cap body that has a top plate and a cylindrical portion that drops vertically from the circumferential edge thereof, and on the cylindrical portion provides a knurl portion and a non-knurl portion that are formed so as to be arranged in the circumferential direction; a plurality of knurl indentations formed at intervals in the circumferential direction of the knurl portion; knurl portion vent holes that are formed on a portion of or the whole of the knurl indentations; and non-knurl portion vent hole in the non-knurl portion that is formed having circumferential length that is longer than that of the knurl portion vent holes.

In this cap, preferably the external diameter of the lower edge portion of the non-knurl portion vent holes is equal to or less than the external diameter of the upper edge portion, and there is an enlarged diameter part that is formed below the lower edge portion of the cylindrical portion and has an outer diameter that is equal to or greater than the outer diameter of the upper edge portion.

Preferably this cap provides a threaded portion that is formed on the cylindrical portion.

Another embodiment of the present invention is a cap providing a cap body that has a top plate and a cylindrical portion that drops vertically from the circumferential edge thereof, and provides a knurl portion and non-knurl portion that are formed arranged in the circumferential direction on the cylindrical portion; a plurality of knurl indentations that are formed at intervals in the circumferential direction on the knurl portion; and at least one non-knurl portion vent hole in the non-knurl portion that is formed having circumferential length that is longer than that of the knurl indentations.

In this cap, preferably the external diameter of the lower edge portion of the non-knurl portion vent holes is equal to or less than the external diameter of the upper edge portion, and there is an enlarged diameter part that is formed below the lower edge portion of the cylindrical portion and has an outer diameter that is equal to or greater than that of the outer diameter of the upper edge portion.

Preferably this cap provides a threaded portion formed in the cylindrical portion.

Yet another aspect of the present invention is a closure device that provides a container that is filled with a liquid content (such as a beverage) and the cap described above coupled on the opening thereof.

A beverage that can ferment is an example of such a liquid content.

The cap of the present invention has the following effects.

(1) In the case in which the cap is resealed after having been opened, the pressure inside the container becomes high due to, for example, the fermentation of the liquid content.

In this regard, with the cap of the present invention, because a long vent hole is formed in the non-knurl portion, when the pressure inside the container becomes high, the cylindrical portion deforms such that the gap in the non-knurl portion vent hole widens, and the gas inside the container is vented from the gaps that occur between the cap and the container to be released to the outside through the vent hole.

Therefore, it is possible to prevent the pressure in the container from rising excessively.

In addition, it is possible to prevent the cap from separating due to the pressure inside the container during opening, which is referred to as “blowing off”.

(2) With the cap of the present invention, because a long vent hole is formed in the non-knurl portion, the upper edge portion of the vent hole cannot project outward greatly from the other parts (the parts that include the lower edge portion).

Thus, when the user grasps and rotates the cap, the fingers do not readily feel the upper edge portion of the vent hole.

Therefore, it is possible to prevent injury to the fingers of the user, and it is possible to increase safety. In addition, the user will not experience discomfort.

In contrast, in a cap in which a long vent hole is formed in the knurl portion, when the user grasps and rotates the cap, a portion of the fingers is caught in the indentation of the knurl portion, and the upper edge portion of the vent holes can be easily felt.

(3) According to the structure in which the external diameter of the lower edge portion of the non-knurl portion vent hole is equal to or less than the external diameter of the upper edge portion, and the enlarged diameter part, which has an external diameter that is equal to or greater than the external diameter of the upper edge portion, is formed below the lower edge portion, when the user grasps and rotates the cap, the fingers do not readily feel the upper edge portion and the lower edge portion.

Therefore, it is possible to prevent injury to the fingers of the user, and it is possible to increase the safety further.

(4) When the threaded portion is formed in the cylindrical portion, the cylindrical portion is pressed inward by the cap coupling device.

In the cap of the present invention, because a long vent hole is formed in the non-knurl portion, when the threaded portion is formed, a deformation in which the part that includes the lower edge portion is shifted inward occurs with difficulty.

Thus, it is possible to prevent the upper edge portion from projecting outward greatly from the other parts.

Therefore, it is possible to prevent injury to the fingers of the user, and it is possible to increase the safety.

In contrast, in a cap having a long vent hole formed in the knurl portion, a deformation in which the indentations of the knurl portion shift further inward due to the pressure applied to the cylindrical portion when the threaded portion is formed occurs easily.

In this case, because the part that includes the lower edge portion of the vent holes shifts inward, the upper edge portion protrudes outward greatly from the other parts, and when the user grasps and rotates the cap, a portion of the fingers can readily feel the upper edge portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an example of the cap of the present invention.

FIG. 2 is a sectional view of the cap shown in FIG. 1.

FIG. 3 is a partial sectional view of the cap shown in FIG. 1.

FIG. 4 is a partial sectional view of the cap shown in FIG. 1.

FIG. 5 is an enlarged sectional view of the essential components showing the state before the coupling of the cap shown in FIG. 1.

FIG. 6 is a frontal view of another example of the cap of the present invention.

FIG. 7 is a schematic view of a testing method.

FIG. 8 is a partial sectional view of the cap of the comparative example.

DESCRIPTION OF THE PREFERD EMBODIMENTS

FIG. 1 to FIG. 4 show the closure device that uses an example of the cap of the present invention. The closure device shown here is formed by a container 30 and a cap 1 that is coupled to an opening 31 thereof.

The container 30 is formed from a metal such as aluminum, aluminum alloy, or steel, and an opening end portion 31 a of the container opening 31 has a shape that is curved outward.

Note container is formed from synthetic resins such as polyethylene terephthalate (PET) and glass can be used.

The cap 1 provides a cap body 4 including of a circular top plate 2 and a cylindrical portion 3 that drops vertically from the circumferential edge thereof, and a liner 5 that is provided on the inner surface of the top plate 2.

The cylindrical portion 3 is divided by a horizontal score 6 (attenuated line) into a main portion 8 that is above the horizontal score 6 and a tamper evidence ring portion 9 (TE ring portion 9) that is joined to the lower edge of the main portion 8 by bridges 7.

A threaded portion 10 is formed on the cylindrical portion 3 when the cap 1 is coupled to the container opening 31. The threaded portion 10 is formed such that the shape conforms to a male thread 32 of the container opening 31.

The lower portion of the TE ring portion 9 is a skirt portion 11 that is curved inward along a bulging step portion 33 of the container opening 31, and engages the bulging step portion 33 during opening.

As shown in FIG. 1 and FIG. 4, a knurl portion 15 is formed on the upper portion of the cylindrical portion 3.

The knurl portion 15 is formed in order to prevent slipping when the cap 1 is grasped and rotated, and includes a plurality of knurl indentations 12 formed at intervals in the circumferential direction and non-formation portions 19, which is the part between adjacent knurl indentations 12.

To obtain a sufficient anti-slipping effect, it is suitable to make the length of base portions 12 a of the knurl indentations 12 in the axial direction of the cap equal to or greater than 1.5 mm (preferably, equal to or greater than 2 mm).

The knurl indentations 12 are preferably formed at regular intervals at substantially constant height position (position in the axial direction of the cap).

The knurl portion 15 is formed in a knurl formation area 13, which corresponds to a portion of the circumference of the cylindrical portion 3.

Knurl portion vent holes 16 (first vent holes), which vent the gas in the cap body 4 to the outside, is formed on the uppermost portion of each of the knurl indentations 12.

Preferably, a knurl portion vent hole 16 has a slit shape that extends in the circumferential direction.

The length (the length “A” shown in FIG. 1) of a knurl portion vent hole 16 in the circumferential direction of the cap can be made, for example, 1 to 4 mm. This length “A” corresponds to the length of a knurl indentation 12 in the circumferential direction.

As shown in FIG. 4, lower edge portions 16 a of the knurl portion vent holes 16 are positioned more inward in the radial direction of the cap than upper edge portions 16 b.

As shown in FIG. 1, the knurl indentations 12 are not formed in the area outside the knurl formation area 13, that is, an area 14 corresponding to the other portion of the circumference of the cylindrical portion 3.

In this area 14, the part of the height position in the axial direction of the cap that is substantially identical to the knurl indentations 12, that is, the part between a knurl indentation 12 b and a knurl indentation 12 c, is called a non-knurl portion 18.

The non-knurl portion 18 is longer in the circumferential direction compared to the non-formation portion 19 in the knurl portion 15 (the part between adjacent knurl indentations 12). The non-knurl portion 18 is formed at a position arranged in the circumferential direction of the knurl portion 15.

As shown in FIG. 1 and FIG. 3, in the cap 1, a non-knurl portion vent hole 17 (a second vent hole) is formed at the non-knurl portion 18.

The non-knurl portion vent hole 17 preferably has a slit shape that extends in the circumferential direction. In the illustrated example, the non-knurl portion vent hole 17 is formed at a height position in the axial direction of the cap that is substantially identical to the knurl portion vent holes 16.

The number of the non-knurl portion vent hole 17 can be 1 or 2 or more. In the illustrated example, there is one non-knurl portion vent hole 17.

As shown in FIG. 1, the non-knurl portion vent hole 17 is formed so as to be long in the circumferential direction of the cap in comparison to a knurl portion vent hole 16. Specifically, the length (length “B” shown in FIG. 1) of the non-knurl portion vent hole 17 is longer than the length “A” of a knurl portion vent hole 16.

If the non-knurl portion vent hole 17 is too short, the effect of lowering the pressure inside the container becomes insufficient, and if it is too long, the air-tightness decreases.

Thus, the length “B” of the non-knurl portion vent hole 17 is preferably 5% to 15% (more preferably 6% to 13%) of the circumferential length of the cylindrical portion 3. It is appropriate that the length “B” be made 5 to 20 mm (preferably, 8 to 15 mm).

By maintaining the length “B” within the range described above, it is possible to prevent the pressure inside the container from rising excessively, and furthermore, it is possible to obtain a sufficient air-tightness.

The length “B” can be set such that the gas in the container 30 is vented to the outside when the internal pressure of the container 30 reaches 70 to 150 psi (0.48 to 1.03 MPa)(gauge pressure; the same applies hereinafter).

As shown in FIG. 3, the external diameter of a lower edge portion 17 a of the non-knurl portion vent hole 17 is preferably equal to or less than the external diameter of an upper edge portion 17 b. In the illustrated example, the external diameter of the lower edge portion 17 a is smaller than the external diameter of the upper edge portion 17 b.

An enlarged diameter part 20 that projects outward in an annular shape is formed below the lower edge portion 17 a in the cylindrical portion 3. The external diameter of the enlarged diameter part 20 is preferably equal to or greater than the external diameter of the upper edge portion 17 b.

The vertical interval (the size difference “C” shown in FIG. 3) in the axial direction of the cap between the upper edge portion 17 b of the non-knurl portion vent hole 17 and the enlarged diameter part 20 should be equal to or less than 1.5 mm (preferably, equal to or less than 1 mm).

Preferably, the cap body 4 is made, for example, from aluminum, aluminum alloy, or steel.

Specifically, when the inner diameter of the cap body 4 is 35 to 40 mm and the thickness is 0.2 to 0.3 mm, preferably the material used in the cap body 4 has a tensile strength (as stipulated in JIS Z2241) is equal to or greater than 200 N/mm² (more preferably, equal to or greater than 205 N/mm²). This tensile strength is preferably equal to or less than 250 N/mm².

By using this material, when the internal pressure of the container 30 becomes high, the cylindrical portion 3 easily deforms such that the gap of the vent hole 17 widens, and the gas inside the container 30 is vented smoothly. Furthermore, during normal usage, when the internal pressure is not high, a sufficient air-tightness can be obtained.

A comparatively soft synthetic resin material such as a blend of polypropylene and rubber, polyethylene, EVA (ethylene vinyl acetate) or the like can be used for the liner 5.

FIG. 5 shows a pre-coupled cap 1 a, which is the state before being coupled to the container opening 31.

In the pre-coupled cap 1 a, an overhead part 22, which is the part that is directly above the upper edge portion 17 b of the non-knurl portion vent hole 17, preferably is formed such that the cross-section forms a substantially straight line along the axial direction of the cap.

The overhead part 22 is the part between a joining part 21 (the curved part that joins the top plate 2 and the cylindrical portion 3) and the upper edge portion 17 b.

By forming the overhead part 22 so as to be a straight line in cross-section, when forming the pre-coupled cap 1 a, it is possible to prevent the overhead part 22 from deforming inward.

Preferably, the joining part 21 in the pre-coupled cap 1 a is formed such that the radius of curvature “R” is equal to or less than 1.5 mm (more preferably, equal to or less than 1.3 mm).

Thereby, when forming the pre-coupled cap 1 a, it is possible to prevent the overhead part 22 from deforming inward.

Preferably, the height position of the non-knurl portion vent hole 17 in the pre-coupled cap 1 a is formed such that the vertical interval (the vertical interval “D” shown in FIG. 5) between the upper edge portion 17 b of the non-knurl portion vent hole 17 and the upper surface of the top plate 2 is 2.5 to 2.8 mm.

By maintaining this vertical interval within this range, when forming the pre-coupled cap 1 a by the cap coupling device, it is possible to prevent the overhead part 22 from deforming inward.

Next, the method of using the closure device that uses the cap 1 will be explained.

To fill the container 30 with a liquid content such as a beverage, it is possible to use a heat filling that is normally carried out under temperature conditions equal to or greater than 80° C. It is also possible to use room temperature aseptic filling that is carried out under room temperature conditions using the container 30 and cap 1 that have undergone sterilization treatment in advance.

In addition, by sealing nitrogen in the container 30 by using a liquid nitrogen supply or the like, it is possible to increase the pressure inside the container. The pressure inside the container can be set such that the pressure at room temperature is a value that exceeds the normal pressure (for example, an amount of 0.1 to 0.3 MPa, which does not deform the cap 1).

To couple the cap 1 to the container opening 31, the following method can be used.

While covering the container opening 31 with the pre-coupled cap 1 a and applying a downward load (top load) to the top plate 2 by the pressure block of the cap coupling device, the cylindrical portion 3 is pressed inward by the threaded portion formation roller (not illustrated), and thereby the threaded portion 10 having a shape that conforms to the male thread 32 is formed.

Then the bottom portion of the TE ring portion 9 is pressed and curved inward by the skirt portion formation roller (not illustrated), the skirt portion 11 is formed, and thereby the cap 1 shown in FIG. 1 is obtained.

To clean the container opening 31, cleaning water is supplied and introduced into the cap 1 through the vent holes 16 and 17.

When the cap 1 that has been coupled to the container opening 31 is rotated in the opening direction, the cap 1 rises, the liner 5 is separated from the opening end portion 31 a, and the seal of the container 30 is broken.

Because the knurl portion 15 is formed on the cap 1, slipping occurs with difficulty when the user grasps and rotates the cap 1.

In the process of opening the cap, because the skirt portion 11 of the TE ring portion 9 engages with the bulging step portion 33, while the main portion 8 rises due to the rotation, the upward motion of the TE ring portion 9 is obstructed.

Thereby, a tensile force acts on the bridges 7 that join the main portion 8 and the TE ring portion 9, the bridges 7 are broken, and the main portion 8 is cut away from the TE ring portion 9.

In the case in which the cap 1 is resealed after having been opened, the pressure inside the container 30 may become extremely high due to fermentation of the liquid content or the like (for example, may become equal to or greater than 0.4 MPa).

When the pressure inside the container 30 becomes high, an upward force is applied to the top plate 2 and the liner 5.

Because the non-knurl portion vent hole 17 that is long in the circumferential direction is formed on the cap 1, when the top plate 2 and the liner 5 are subjected to the upward force, the cylindrical portion 3 deforms such that the gap of the non-knurl portion vent hole 17 widens, and at the same time, the top plate 2 and the liner 5 near the deforming part rise, the liner 5 is separated from the opening end portion 31 a.

In addition, a gap occurs between the liner 5 and the opening end portion 31 a. The gas in the container 30 is vented outside the container 30 through this gap, and then vented to the outside of the cap 1 through the vent holes 16 and 17.

The function of the closure device described above is characteristically exhibited when filled with a content that can ferment.

Examples of the contents (beverage) that can ferment are non-carbonated beverages such fruit drink, tea, and coffee beverages, which that include much organic matter (such as sugar) that may act as fermentation agents.

It is possible to obtain a closure device having a beverage inside by filling the container 30 with a beverage and coupling the cap 1 to the opening 31.

Note that carbonated beverages (a beverage that incorporates carbon dioxide gas in advance) ferment with difficulty because the oxygen concentration is low and microorganisms grow with difficulty. Thus, the carbonated beverages, even though a beverage that can ferment is not included, are possible to be applied the present invention.

The cap 1 has the following effects.

(1) In the case in which the cap 1 is resealed after having been opened, the pressure in the container becomes high due to the fermentation of the liquid content and the like.

With the cap 1, because the non-knurl portion vent hole 17 that is long in the circumferential direction is formed in the non-knurl portion 18, when the pressure in the container becomes high, the cylindrical portion 3 deforms such that the gap of the non-knurl portion vent hole 17 widens, and the liner 5 that is near the deforming part is separated from the open end part 31 a. The gas inside the container 30 is vented through between the liner 5 and the open end part 31 a, and discharged to the outside through the vent holes 16 and 17.

Therefore, it is possible to prevent the pressure inside the container 30 from rising excessively.

In addition, it is possible to prevent the cap from coming off due to the pressure inside the container during opening, which is referred to as “blowing off”.

(2) Because the non-knurl portion vent hole 17 is formed on the non-knurl portion 18, the upper edge portion 17 b of the non-knurl portion vent hole 17 does not project outward greatly from the other parts (parts that include the lower edge portion 17 a).

Thus, when the user grasps and rotates the cap 1, the fingers do not readily feel the upper edge portion 17 b of the non-knurl portion vent hole 17.

Therefore, it is possible to prevent injury to the fingers of the user, and it is possible to increase the safety. In addition, the user does not experience discomfort.

In contrast, in a cap in which a long vent hole is formed in the knurl portion, when the user grasps and rotates the cap, a portion of the fingers is caught in the indentation of the knurl portion, and the upper portion of the vent hole can be easily felt.

(3) Because the external diameter of the lower edge portion 17 a of the non-knurl portion vent hole 17 is equal to or less than the external diameter of the upper edge portion 17 b, and the enlarged diameter part 20, which has an external diameter that is equal to or greater than the external diameter of the upper edge portion 17 b, is formed below the lower edge portion 17 a, when the user grasps and rotates the cap 1, the fingers do not readily feel the upper edge portion 17 b and the lower edge portion 17 a.

Therefore, it is possible to prevent injury to the fingers of the user, and it is possible to increase the safety further.

(4) When the threaded portion 10 is formed in the cylindrical portion 3, the cylindrical portion 3 is pressed inward by the cap coupling device.

In the cap 1, because the non-knurl portion vent hole 17 is formed in the non-knurl portion 18, when the threaded portion 10 is formed, a deformation in which the part that includes the lower edge portion 17 a is shifted inward occurs with difficulty.

Thus, it is possible to prevent the upper edge portion 17 b from projecting outward greatly from the other parts (the part that includes the lower edge portion 17 a).

Therefore, it is possible to prevent injury to the fingers of the user, and it is possible to increase the safety.

In contrast, in a cap in which a long vent hole is formed in the knurl portion, a deformation in which the indentations of the knurl portion shift further inward due to the pressing force applied to the cylindrical portion occurs easily when the threaded portion is formed.

In this case, because the part that includes the lower edge portion of the vent hole shifts inward, the upper edge portion projects outward greatly from the other parts, and when the user grasps the cap, a portion of the fingers can readily feel the upper edge part.

In the cap 1 shown in FIG. 1, the knurl portion vent hole 16 is formed on all of the knurl indentations 12, but the present invention is not limited thereby. For example, the knurl portion vent hole can be formed in only some of the knurl indentations, or the knurl portion vent hole can be omitted from the knurl indentations.

The cap 41 shown in FIG. 6 differs from the cap 1 shown in FIG. 1 on the point that a knurl portion vent hole 16 is not formed in the knurl indentation 12.

In the cap 41, at the knurl formation area 13, a vent hole can be formed between the adjacent knurl indentations 12 (the non-formation portion 19).

EXAMPLE 1

The cap 1 shown in FIG. 1 was manufactured.

In the knurl formation area 13, twenty-six knurl indentations 12 were formed at regular intervals, and a slit shaped knurl portion vent hole 16 (length: 1.2 mm) was formed in each of these knurl indentations 12.

In the non-knurl portion 18 (length: 15 mm), a slit shaped non-knurl portion vent hole 17 (length: 9.5 mm) was formed in the circumferential direction.

As shown in FIG. 3, the enlarged diameter part 20 was formed such that the external diameter was larger than the external diameter of the upper edge portion 17 b.

The external diameter of the cap 1 was 38 mm.

An aluminum alloy 5151 (tensile strength: 251 N/mm²) stipulated by JIS was used as the material for the cap body 4.

The following tests were carried out on the cap 1.

As shown in FIG. 7, the cap 1 was coupled to the container opening 31, the part of the cylindrical portion 3 that includes the non-knurl portion vent hole 17 was pressed against a specimen 23, and maintaining this state, was moved in the axial direction (the direction of the arrow in the figure) of the cap. As specimens, cylindrical boiled fish paste or fish meat sausages were used.

The weight of the specimen 23 before and after testing was measured, and the decrease in the weight after testing was calculated. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1

As shown in FIG. 8, a cap 51 was manufactured. A second knurl portion 24, which is a long indentation in the circumferential direction, was formed on this cap 51 at a position corresponding to the non-knurl portion 18 in the cap 1 of example 1.

A second knurl portion vent hole 25 was formed in the second knurl portion 24 that had the same length as the non-knurl portion vent hole 17. Unlike the example, the enlarged diameter part 20, which has an external diameter that is larger than that of the upper edge portion 25 b of the knurl portion vent hole 25, was not formed. Other aspects of the structure are identical to those of the cap 1 in the example 1.

The depth of the second knurl portion 24 was approximately 0.3 mm, similar to the depth of the knurl indentation 12.

Similar to example 1, the following tests were carried out on the cap 51.

The cap 51 is coupled to the container opening 31, the part of the cylindrical portion 3 that includes the second knurl portion vent hole 25 was pressed against the specimen 23, and maintaining this state, moved in the axial direction of the cap (the direction of the arrow in the figure). As specimen 23, cylindrical boiled fish paste or fish meat sausage were used.

The weight of the specimens 23 before and after testing was measured, and the decrease in the weight after testing was measured. The results are shown in Table 1. TABLE 1 Example 1 Comparative Example 1 Specimen Weight (g) Amount of Specimen Weight (g) Amount of Before After Decrease Before After Decrease Sample No. Specimen Testing Testing (g) Testing Testing (g) 1 boiled 33.58 33.57 0.01 34.49 34.46 0.03 2 fish paste 33.57 33.56 0.01 34.46 34.42 0.04 3 33.56 33.54 0.02 34.42 34.37 0.05 4 33.54 33.52 0.02 34.37 34.33 0.04 5 33.52 33.51 0.01 34.33 34.3 0.03 6 fish 27.76 27.75 0.01 29.39 29.34 0.05 7 sausage 27.75 27.73 0.02 29.34 29.28 0.06 8 27.73 27.72 0.01 29.28 29.23 0.05 9 27.72 27.7 0.02 29.23 29.18 0.05 10 27.7 27.69 0.01 29.18 29.12 0.06

As shown in Table 1, in the example 1, in which the non-knurl portion vent hole 17 having the enlarged diameter part 20 was formed in the cap 1, only a very small amount of the specimen was shaved off by the cap 1, and thus the specimen weight after testing did not change greatly.

In contrast, in comparative example 1, in which the second knurl portion vent hole not having the enlarged diameter part 20 is formed in the cap 51, the weight of the specimen after testing decreased greatly.

This can be considered to be due to the upper edge portion 25 b of the second knurl portion vent hole 25 projecting greatly from the other parts because there was no enlarged diameter part 20 in the cap 51. A significant amount of the specimen was off by this part.

From these results, with the cap 1 of example 1, it can be understood that it is possible to increase the safety when the user grasps and rotates the cap 1.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims. 

1. A cap having a top plate and a cylindrical portion that drops vertically from a circumferential edge thereof, the cap comprising: knurl portions and a non-knurl portion that are formed in the cylindrical portion arranged in a circumferential direction of the cap; a plurality of knurl indentations formed in the knurl portion at intervals in the circumferential direction of the cap; a knurl portion vent hole formed on at least some of the plurality of knurl indentations; and a non-knurl portion vent hole formed in the non-knurl portion and having a circumferential length that is longer than that of the knurl portion vent hole.
 2. A cap according to claim 1, wherein the non-knurl portion vent hole has a lower edge portion whose external diameter is equal to or less than the external diameter of the upper edge portion, and the cap further comprising an enlarged diameter part that is formed below the lower edge portion of the cylindrical portion and that has an external diameter that is equal to or greater than the external diameter of the upper edge portion.
 3. A cap according to claim 1, further comprising a threaded portion that is formed in the cylindrical portion.
 4. A closure device comprising a container that is filled with a content and a cap according to claim 1 coupled to an opening portion thereof.
 5. A closure device according to claim 4, wherein the content may ferment.
 6. A cap having a top plate and a cylindrical portion that drops vertically from a circumferential edge thereof, comprising: knurl portions and a non-knurl portion that are formed in the cylindrical portion arranged in a circumferential direction of the cap; a plurality of knurl indentations formed in the knurl portion at intervals in the circumferential direction of the cap; and a non-knurl portion vent hole formed in the non-knurl portion and having a circumferential length that is longer than that of the knurl indentations.
 7. A cap according to claim 6 wherein the non-knurl portion vent hole has a lower edge portion whose external diameter is equal to or less than an external diameter of an upper edge portion; and the cap further comprising an enlarged diameter part that is formed below the lower edge portion of the cylindrical portion and that has an external diameter that is equal to or greater than the external diameter of the upper edge portion.
 8. A cap according to claim 6, further comprising a threaded portion that is formed in the cylindrical portion.
 9. A closure device comprising a container that is filled with a content and a cap according to claim 6 coupled to an opening portion thereof.
 10. A closure device according to claim 9, wherein the content may ferment. 